The present invention relates to method and system for pulse communication which has a large signal transmission speed and a large transmission capacity and yet is capable of monitoring the signal transmission line, and, more particularly, to method and system for pulse communication suitable for optical pulse communication by optical fibers.
FIG. 1 illustrates the principle of a heretofore used pulse communication systems. The heretofore known pulse communication systems included a 2-level pulse communication system in which data signals were transmitted by logical 0 and 1 as shown in FIG. 1(a) and an envelope modulation pulse communication system in which repetition pulses were subjected to envelope modulation as shown in FIG. 1(b). The 2-level pulse communication had a disadvantage that it was unable to determine whether absence of a data signal denoted one of the 2-level pulse signal or some trouble in the signal transmission line. Further, in the case where a transmission line monitor signal had to be inserted in the pulse signal of high speed, the 2-level pulse communication system had a further disadvantage that the apparatus had to be large in construction to detect the phase of the signal accurately. On the other hand, the envelope modulation pulse communication system had a disadvantage that the signal transmission speed was lower than the pulse repetition frequency.
Accordingly, an object of the present invention is to provide method and system for pulse communication which is simple in circuit construction and yet large in signal transmission capacity and capable of transmitting clock signals and transmission line monitor signals with the transmission data signals by converting the transmission data signal into a CMI (Coded Mark Inversion) code and further converting it into a 3-level CMI code for transmission.